Road paver with a radar-based leveling device and control method

ABSTRACT

A road paver according to the disclosure comprises a material hopper for receiving paving material and a screed for compacting paving material that is supported with towing arms on a chassis of the road paver. In addition, a radar sensor unit is provided that is configured to measure the distances between the radar sensor unit and at least two ground positions. A control unit of the road paver is configured to adjust a position of the screed relative to the chassis based on the distances measured. In addition, a corresponding method for controlling a road paver is specified.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims foreign priority benefits under 35 U.S.C. §119(a)-(d) to European patent application number EP 15 180 954.8, filed Aug. 13, 2015, which is incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the technical field of road pavers. The disclosure relates in particular to road pavers with a screed for compacting paving material and a method for controlling such road pavers.

BACKGROUND

In road pavers, the screed is advantageously not rigidly connected to the chassis but suspended thereon by towing arms. The screed is there floatingly supported by the paved material or the material to by paved. To control the thickness and evenness of the layer to be paved, an inclination angle of the screed can be changed in a known manner via the towing arms. In order to meet given requirements for thickness and/or evenness of the layer to be paved, road pavers can be equipped with suitable control systems for the position of the screed relative to the chassis, so-called leveling systems. In such a control system, the relative position of the screed relative to a reference, for example an already paved part of the pavement or a roadbed that is to be provided with the pavement, must be determined.

From EP 0 542 297 A1, a road paver with ultrasonic sensors mounted on a support is known. At least three ultrasonic sensors are provided for determining the distances between the sensors and a reference surface. To compensate for local unevenness of the reference surface, the sensors should be spaced as far apart as possible in the direction of travel of the road paver. The associated large size of the support for the ultrasonic sensors extending in the direction of travel of the road paver is disadvantageous both in terms of handling the road paver as well as the relatively high effort for the installation and removal of the support.

An alternative height sensor for a road paver is known from DE 100 60 903 A1. There, three laser measuring heads are each directed towards spaced measuring points on a reference surface. The distance of the laser measuring heads relative to the reference surface is determined by way of the signals that are emitted by the laser measuring heads and again detected after being reflected from the reference surface, and the screed is actuated based thereupon.

SUMMARY

It is an object of the present disclosure to improve a road paver or a method for controlling a road paver with respect to the leveling quality and manageability during the paving process.

A road paver according to the disclosure comprises a material hopper which is in the direction of travel of the road paver preferably located toward the front for receiving the paving material. The paving material can by way of a conveyor device provided on the road paver be brought in front of a screed that is towed behind the road paver. The paving material can there by way of a typically provided distribution auger be distributed perpendicular to the direction of travel of the road paver in order to obtain a uniform amount of paving material over the entire paving width. The screed of the road paver according to the disclosure is provided for compacting the paving material and is held with towing arms on a chassis of the road paver.

The road paver according to the disclosure furthermore comprises a radar sensor unit which is configured to measure the distances between the radar sensor unit and at least two ground positions. The ground positions are positions that are not located on the road paver. The ground positions can be positions on the stretch intended for paving or also be located adjacent to the stretch. The road paver also comprises a control unit which is configured to adjust a position of the screed relative to the chassis based on the distances measured. The control unit can for this purpose be configured to actuate one or more hydraulic cylinders for adjusting a pivot point of the towing arms on the chassis.

The radar sensor unit can measure the distances between the radar sensor unit and the at least two ground positions in that it emits radar beams directed toward each one of the ground positions and detects the beams that are reflected back. The distance to the respective ground position can be determined with a pulsed radar due to the time difference between emission and detection. It is also conceivable to provide a non-pulsed radar with continuous emission of radar beams, where distance measurement is possible, for example, by way of evaluating a Doppler effect.

Distance measurement by way of a radar sensor unit also works very well over long distances, whereas, for example, ultrasonic sensors must be located as close as possible (about 30 cm) from the ground position to be measured for sufficiently accurate measurements. It is therefore in the present disclosure not required that a projecting support for sensor units be provided at the road paver for measuring ground positions that are spaced far apart. On the contrary, different ground positions at great distances to each other can be measured even with a compact and localized radar sensor unit. For example, two consecutive ones of said at least two ground positions can have a minimum distance of less than 10 cm, 20 cm, 50 cm, 1 m, 2 m, 5 m, 10 m or 20 m. The entire measuring range of the radar sensor unit, i.e., the greatest distance between two of the at least two ground positions can be, for example, more than 10 m, more than 15 m or more than 20 m. The distances specified between the ground positions can relate to a stationary road paver or a road paver during a paving process.

It has surprisingly shown that with the radar-based measurement method according to the invention, the distances are detected more reliably and accurately than with a laser system.

The at least two ground positions are preferably located on a common straight line parallel to the paving direction of travel of the road paver. The course of the ground level over a certain distance can thereby be taken into account for adjusting the position of the screed and local unevenness has less influence on the outcome of the leveling process. This outcome can be further improved if the distances are measured between the radar sensor unit and more than two, in particular more than five, more than 10, more than 20, more than 30, more than 50, more than 100 or more than 150 ground positions.

Due to the long-distance nature of radar-based measurement, the radar sensor unit can be mounted in a compact manner to a mast, preferably to a vertical mast, attached to the chassis, a towing arm or the screed or any other part of the road paver.

Measuring the distances between the radar sensor unit and the at least two ground positions can be performed, for example, simultaneously or temporally sequentially. A time interval between the measurement of the distances between the radar sensor unit and two consecutive ones of said at least two ground positions can in particular be smaller, preferably by a factor of 20, a factor of 10, a factor of 5 or a factor of 2, than the quotient of the distance between the consecutive ground positions and the velocity of the road paver. It is also conceivable that the time interval between the measurement of the distances between the radar sensor unit and two consecutive ones of said at least two ground positions is less than 50 ms, 1 s, 5 s, 10 s or 30 s.

The radar sensor unit can comprise a radar sensor that is pivotable between at least two measuring positions for measuring the distance between the radar sensor unit and the at least two ground positions. With this radar sensor, the at least two ground positions can be measured temporally consecutively. Due to such an arrangement, measuring a plurality of ground positions is possible with only one radar sensor. The temporal delay between measurements has no negative effect due to the slow paving speed of road pavers of a few meters per minute.

The radar sensor unit can comprise a radar sensor with an antenna and a radome. The radome can be configured to focus beams emitted by the antenna and can be pivoted between at least two measuring positions in which the beams are each focused to different ones of the at least two ground positions. Here as well, only a single radar sensor is needed for measuring the different ground positions. Due to the focusing function of the radome, it is sufficient to pivot the radome so that the radar sensor as a whole does not need to be pivotable. The radome can at the same time also act as a protective cover for the radar sensor and as focusing element.

It is also conceivable that the radar sensor unit comprises a radar sensor with an antenna and a dielectric lens. The dielectric lens can be configured to focus beams emitted by the antenna and can be pivoted between at least two measuring positions in which the beams are each focused to different ones of the at least two ground positions. Here as well, only a single radar sensor is necessary to measure several ground positions.

Alternatively, the radar sensor unit can comprise at least two radar sensors being at fixed angles to each other which are each adapted to measure the distance between the radar sensor unit and one of the at least two ground positions. Each ground position can be assigned its own radar sensor. In such a configuration, all ground positions can be measured simultaneously. However, ground positions can of course also be measured successively by different radar sensors. There are no actuators necessary for pivoting the radar sensors.

For adjusting the position of the screed, the control unit of the road paver can from the measured distances and the known position of the radar sensor unit determine vertical distances between the radar sensor unit and the ground positions. Since furthermore preferably the position, in particular the height position of the radar sensor unit relative to the screed is known, suitable control values for actuators changing the position of the screed can be calculated in order to obtain a desired position of the screed relative to the ground positions. In order to obtain a defined layer thickness, for example, the vertical distance between a trailing edge of the screed and the ground positions can be controlled to a constant and/or a user-predefined value.

The control unit of the road paver can, for example, by use of an average value, take into account all distances measured. A vertical distance can for this be calculated for every distance measured. The vertical distances can then be averaged and the average value can be used for calculating the control value for the position of the screed. Alternatively, a separate control value can be calculated from every calculated vertical distance and an average of the control values can then be determined, where the average value is then used to adjust the screed.

Other approaches are conceivable for obtaining suitable control values for adjusting the position of the screed from the distances measured. For example, the control unit can from the distances measured and the respectively known alignment of the radar sensor unit determine a straight line which describes the position of the ground positions as best possible, for example, by calculating a linear regression line. Based on the regression line and the known position, in particular the height position, of the radar sensor unit relative to the screed, a suitable control value for the position of the screed can be calculated.

In all described variants, it is conceivable to consider distances measured only where they are within a certain predefined range. When adjusting the screed, it can thereby be prevented that false measurements, for example due to people or objects located within the beam path of the radar beams, are taken into account.

The disclosure also relates to a method for controlling the road paver according to the disclosure described above. In the method, the distances between the radar sensor unit and at least two ground positions are measured with the radar sensor unit provided on the road paver. The position of the screed is adjusted relative to the chassis by the control unit of the road paver based on the distances measured. Further embodiments of the method according to the disclosure will be evident to the person skilled in the art from the above description of the road paver.

Embodiments according to the present disclosure are described below in more detail with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a road paver according to the disclosure;

FIG. 2 shows a schematic representation of the incorporation of the radar sensor unit and the control unit into the system of the road paver;

FIG. 3A shows a schematic representation of the radar sensor unit of the road paver of the disclosure according to one embodiment;

FIG. 3B shows a schematic representation of the radar sensor unit of the road paver of the disclosure according to another embodiment;

FIG. 3C shows a schematic representation of the radar sensor unit of the road paver of the disclosure according to a further embodiment; and

FIG. 3D shows a schematic representation of the radar sensor unit of the road paver of the disclosure according to yet a further embodiment.

DETAILED DESCRIPTION

As required, detailed embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary and that various and alternative forms may be employed. The figures are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art.

FIG. 1 shows a road paver 1 according to the disclosure that moves in the direction of travel F on a ground level. In the direction of travel F toward the front, road paver 1 comprises a material hopper 2 for receiving the paving material. A respective towing arm 4 is in relation to the direction of travel F supported on both sides of road paver 1 via a height-adjustable pivot point 5 on chassis 3 of road paver 1. Pivot point 5 is preferably adjustable in height on chassis 3 by way of a pivotable hydraulic cylinder 6. At a rear side of road paver 1, towing arms 4 are again respectively mounted on both sides via a height-adjustable rear hydraulic cylinder 7 to chassis 3. Screed 8 of road paver 1 is suspended at the rear ends of towing arms 4. An operator station 10 of road paver 1 accommodates an operator and comprises control and display units 12 via which entries can be made to control road paver 1 and system data can be displayed to inform the user.

Road paver 1 according to the disclosure comprises a radar sensor unit 20. It is configured to measure distances d1, d2, d3, d4, d5 between radar sensor unit 20 and at least two ground positions P1, P2, P3, P4, P5. As shown in FIG. 1, ground positions P1-P5 are preferably located on a common straight line parallel to the paving direction of travel F of road paver 1. Radar sensor unit 20 can be mounted on a mast 22 attached to a towing arm 4. It is alternatively conceivable that the mast 22 with the radar sensor unit 20 is attached to chassis 3 or screed 8 or another part of road paver 1. It is also conceivable to directly mount radar sensor unit 20 to road paver 1 without any mast 22.

As shown in FIG. 2, road paver 1 comprises a control unit 30 which via a control line 32 receives the measured distances from radar sensor unit 20. Control unit 30 can then via a further control line 36 actuate pivotable hydraulic cylinder 6 and thereby via towing arms 4 adjust the inclination angle of screed 8. It would also be conceivable that control unit 30 additionally or alternatively can actuate rear hydraulic cylinders 7 in order to change the position of screed 8. Control unit 30 is via a third control line 34 connected to input unit 12 and can receive setpoint values for the paving thickness or the like. It is also conceivable that control unit 30 receives such setpoint values from other sources, for example from a storage unit. Based on the measured distances d1-d5 as well as the setpoints received from input unit 12, control unit 30 calculates control values to be outputted to pivotable hydraulic cylinders 6. According to a preferred embodiment, fully automatic leveling can be achieved in which a setpoint value must be defined only once. However, the setpoint value can also be changed during the paving process.

FIGS. 3A to 3D show various embodiments of radar sensor unit 20. According to the embodiment shown in FIG. 3A, radar sensor unit 20 comprises several (at least two) radar sensors 24 being at fixed angles to each other. They are arranged such that they measure distance d1-d5 between radar sensor unit 20 and respectively one of ground positions P1-P5 to be measured.

According to the alternative embodiment shown in FIG. 3B, radar sensor unit 20 comprises a radar sensor 24 which is pivotable between several measuring positions M1, M2 (two shown) for measuring distances d1-d5 between radar sensor unit 20 and ground positions P1-P5. Thereby, a measuring position M1, M2 respectively corresponds to a ground position P1-P5 to be measured. In order to ensure pivotability of radar sensor 24, the latter can be attached by way of a pivot joint 50 which is preferably controlled by control unit 30.

According to the embodiment shown in FIG. 3C, radar sensor unit 20 comprises a radar sensor 24 with an antenna 26 and a dielectric lens 28. Antenna 26 is configured to emit the radar beams. The same antenna 26 is preferably used to again detect the radar beams reflected from the respective ground positions P1-P5. Dielectric lens 28 is designed and positioned to focus the radar beams emitted by antenna 26. Dielectric lens 28 can be pivoted between several measuring positions M1′, M2′ (two shown), wherein the radar beams emitted by antenna 26 are focused to different ground positions P1-P5 to be measured in the various measuring positions M1′, M2′. Pivoting dielectric lens 28 can be accomplished by a suitable mechanical actuator 50′ which is preferably controlled by control unit 30. To protect antenna 26 and dielectric lens 28 from external influences and fouling, they are preferably housed in a radome 40 that is most permeable to the radar beams.

The mode of operation of the embodiment shown in FIG. 3D is similar to the mode of operation of the embodiment of FIG. 3 c. Here as well, radar sensor unit 20 comprises a radar sensor 24 with an antenna 26 for emitting the radar beams. Preferably the same antenna 26 is employed for detecting the reflected radar beams. Unlike the embodiment of FIG. 3C, however, no dielectric lens is provided. Focusing the radar beams to the respective ground position P1-P5 is effected via radome 40′ covering antenna 26. To enable focusing onto the different ground positions P1-P5, this radome 40′ is povitable between several measuring positions M1″, M2″ (two shown) corresponding to ground positions P1-P5 to be measured, preferably in a manner controlled by control unit 30. Here as well, antenna 26 is protected by radome 40′ from external influences and fouling.

It is understood that radar sensors 24 of radar sensor units 20 shown in FIGS. 3a and 3b each comprise an antenna for emitting the radar beams. Preferably the same antenna is additionally used for detecting the reflected radar beams. However, it is also conceivable to provide the respective radar sensor 24 with an additional antenna for detecting the reflected radar beams.

As one skilled in the art would understand, any of the above described units (e.g., control and display units 12, radar sensor unit 20, control unit 30, etc.) may include suitable hardware and/or software, such as one or more processors (e.g., one or more microprocessors, microcontrollers and/or programmable digital signal processors) in communication with, or configured to communicate with, one or more storage devices or media including computer readable program instructions that are executable by the one or more processors so that the respective unit may perform particular algorithms represented by the functions and/or operations described herein. Any of the above described units may also, or instead, include one or more application specific integrated circuits, programmable gate arrays or programmable array logic, programmable logic devices, or digital signal processors.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms according to the disclosure. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. Additionally, the features of various implementing embodiments may be combined to form further embodiments according to the disclosure. 

What is claimed is:
 1. A road paver comprising: a chassis; a material hopper for receiving paving material; a screed for compacting paving material supported with towing arms on the chassis; a radar sensor unit that is configured to measure distances between the radar sensor unit and at least two ground positions; and a control unit which is configured to adjust a position of the screed relative to the chassis based on the distances measured.
 2. The road paver according to claim 1 wherein the at least two ground positions are located on a common straight line that is parallel to a paving direction of travel of the road paver.
 3. The road paver according to claim 1 wherein the radar sensor unit is mounted to a mast attached to the chassis, one of the towing arms, or the screed.
 4. The road paver according to claim 3 wherein the mast is oriented vertically.
 5. The road paver according to claim 1 wherein the radar sensor unit comprises a radar sensor which is pivotable between at least two measuring positions for measuring the distances between the radar sensor unit and the at least two ground positions.
 6. The road paver according to claim 1 wherein the radar sensor unit comprises a radar sensor with an antenna and a radome, wherein the radome is configured to focus beams emitted by the antenna, and the radome is pivotable between at least two measuring positions in which the beams are respectively focused onto different ones of the at least two ground positions.
 7. The road paver according to claim 1 wherein the radar sensor unit comprises a radar sensor with an antenna and a dielectric lens, and wherein the dielectric lens is configured to focus beams emitted by the antenna, and the dielectric lens is pivotable between at least two measuring positions in which the beams are respectively focused onto different ones of the at least two ground positions.
 8. The road paver according to claim 1 wherein the radar sensor unit comprises at least two radar sensors being at fixed angles to each other and which are each adapted to measure the distance between the radar sensor unit and one of the at least two ground positions.
 9. The road paver according to claim 1 wherein the control unit or the radar sensor unit is configured to average the distances measured between the radar sensor unit and the at least two ground positions.
 10. A method for controlling a road paver with a material hopper for receiving paving material and a screed for compacting paving material that is supported with towing arms on a chassis of the road paver, the method comprising: measuring with a radar sensor unit provided on the road paver distances between the radar sensor unit and at least two ground positions; and adjusting with a control unit a position of the screed relative to the chassis based on the distances measured.
 11. The method according to claim 10 wherein the at least two ground positions are located on a common straight line that is parallel to a paving direction of travel of the road paver.
 12. The method according to claim 10 wherein the radar sensor unit is mounted to a mast attached to the chassis, one of the towing arms, or the screed.
 13. The method according to claim 12 wherein the mast is oriented vertically.
 14. The method according to claim 10 wherein the radar sensor unit comprises a radar sensor, and wherein the measuring comprises pivoting the radar sensor between at least two measuring positions for measuring the distances between the radar sensor unit and the at least two ground positions.
 15. The method according to claim 10 wherein the radar sensor unit comprises a radar sensor with an antenna and a radome, wherein the radome focuses beams emitted by the antenna, and wherein the method comprises pivoting the radome between at least two measuring positions in which the beams are respectively focused onto different ones of the at least two ground positions.
 16. The method according to claim 10 wherein the radar sensor unit comprises a radar sensor with an antenna and a dielectric lens, wherein the dielectric lens focuses beams emitted by the antenna, and wherein the method comprises pivoting the dielectric lens between at least two measuring positions in which the beams are respectively focused onto different ones of the at least two ground positions.
 17. The method according to claim 10 wherein the distances measured between the radar sensor unit and the at least two ground positions are averaged by the control unit or the radar sensor unit. 